So that rectangular piece in the supplied liner is what folds in or out to cover the holes for winter riding? Does the replacement have anything to cover them?
Reading the webBikeWorld review of the C3Pro, they classify it as shaped slightly to the inverse-egg side of neutral, implying that the decreased abduction rate comes from the poor seal formed around the bottom and resulting 'booming' turbulence noise on those with egg-shaped heads.
'06 F650GS Dakar
Those who believe you should always error on the side of caution usually become comfortable making errors and before too long know of little else.